The present invention relates to a pulse tube refrigerating system.
In a conventional pulse tube refrigerating system, a compression space, a radiator, an accumulator and a pulse tube are arranged in series so as to constitute a closed operating space. Within the closed operating space, there is filled an amount of operating fluid such as helium gas, and the pressure of the operating fluid is set to be varied due to the compression at the compression space. This results in an establishment of a phase difference between the pressure vibration and the displacement vibration of the operating fluid, which leads to that a heat is set to be absorbed at a lower temperature terminal or a cold head of the pulse tube and the resulting heat is radiated from the radiator. Thus, the lower temperature terminal or the cold head of the pulse tube is cooled or lowered at a set temperature.
In order to improve the thermal transfer ability, it is well known that the setting of the phase difference at about 90 degrees is effective. This fact can be known from a thesis, for example, reported in "Advances in Cryogenic Engineering, Vol. 35, P1191/1990). On the basis of this, an improved pulse tube refrigerating system has been proposed in a report (Proc. Fifth International Cryocooler conf. (1988) P.127). In the improved pulse tube refrigerating system, a phase shifter includes a buffer tank which is used as a Helmholtz resonator and the resultant resonant frequency .omega..sub.0 is set to be more than the driving or fluctaion frequency .omega. of the operating fluid in order to establish the phase difference of about 90 degrees between the pressure vibration and the displacement vibration of the operating fluid as possible, thereby improving the heat transfer ability of the accumulator.
However, in the foregoing apparatus or device, the driving or fluctaion frequency of the operating fluid is restricted by the resonant frequency of the phase shifter, resulting in that foregoing apparatus is not so flexible for the practical use.